Polylactic acids (PLA) are aliphatic polyesters and are considered useful biodegradable materials because of their hydrolytic property. Additionally, the degradative product of polylactic acid (i.e., lactic acid) is readily absorbed in vivo. As such, PLA is commonly used for medical purposes, such as in surgical sutures, in sustained-release capsules in drug delivery systems, and as reinforcing materials for bone fractures. However, conventional processes for forming PLA articles possess undesirable features or attributes, such as, for example, processing above the melt temperature of the PLA polymer that degrades the PLA polymers and undesirably colors the polymer, and reduces physical properties such as tensile strength and matrix modulus. Additionally, conventional process are forced to use low molecular weight PLA due to the high melt viscosity.
Thus, there exists a need in the art for a process for making a PLA polymer and a PLA polymer article that is biodegradable, possesses a high modulus of elasticity, and has increased tensile strength.